ATMOSPHERIC AIR AS THE FOOD OF PLANTS. 93 
of fuel is thoroughly ignited. When, on the other hand, the fire is cov- 
ered with cold fuel, carbonic oxide escapes copiously into the atmos- 
phere. 
When crystallized oxalic acid is heated with oil of vitriol, it yields 
water to the latter, and falls iuto a mixture of carbonic acid and carbonic 
oxide. 
c, 8,0, 20,0""=- €0; ‘+-:CO' + “3 HO. 
Carbonic oxide may, perhaps, be formed in small quantity in the de- 
cay of organic matters; though Corenwinder (Compt. Rend., LX, 102) 
failed to detect it in the rotting of manure. 
Relations of Carbonic Oxide to Vegetation.—<Ac- 
cording to Saussure, while pea-plants languish and die when immersed 
in carbonic oxide, certain marsh plants (Zpilobium hirsutum, Lythrimn 
salicaria, and Polygonum persicaria) flourish as well in this gas as in com- 
mon air. Saussure’s experiments with these plants lasted six weeks. 
There occurred an absorption of the gas and an evolution of oxygen. 
It is thus to be inferred that carbonic oxide may be a source of carbon 
to aquatic plants. 
Boussingault (Compt. Rend., LX1, 493) was unable to detect any action 
of the foliage of land plants upon carbonic oxide, either when the gas 
was pure or mixed with air. 
The carbonic oxide which Boussingault found in 1863 in air exhaled 
from submerged leaves, proves to have been produced in the analyses, 
(from pyrogallate of potash,) and was not emitted by the leaves them- 
selves, as at first supposed, as both Cloez and Boussingault have shown, 
Nitrous Oxide, N,O.—This substance, the so-called laughing 
gas, is prepared from nitrate of ammonia by exposing that salt to a heat 
somewhat higher than is necessary to fuse it. The salt decomposes into 
nitrous oxide and water. 
NH,, NO; — N,O RE 2 H,.O. 
The gas is readily soluble in water, and has a sweetish odor and taste. 
When breathed, it at first produces a peculiar exhilarating effect, which 
is followed by stupor and insensibility. 
This gas has never been demonstrated to exist in the atmosphere. In 
fact, our methods of analysis are incompetent to detect it, when it.is 
present. in very minute quantity in a gaseous mixture. Knop is of the 
opinion that nitrous oxide may occur in the atmosphere, aud has pub- 
lished an account of experiments (Journal fiir Prakt. Chem., Vol. 59, 
p. 114) which, according to him, prove that it is absorbed by vegetation. 
Until nitrous oxide is shown to be accessible to plants, any further no- 
tice of it is unnecessary in a treatise of this kind. 
Wydrochloric Acid Gas, HCl, whose properties have been 
described in How Crops Grow, p. 118, is found in minute quantity in the 
air over salt marshes. It doubtless proceeds from the decomposition of 
the chloride of magnesium of sea-water. Sprengel has surmised its ex- 
